Field of the Disclosure
The present disclosure relates to a display device, and more particularly, to a white organic light emitting device having a broader color gamut and an increased lifespan, and an organic light emitting display device using the same.
Description of the Background
Recently, as the information age has fully arrived, the field of displays that visually display electrically conveyed information signals has developed rapidly. In response to this, various kinds of flat panel display devices having excellent characteristics, such as a small thickness, a low weight, and low power consumption, have been developed and have rapidly replaced existing cathode ray tubes (CRTs).
Representative examples of such flat panel display devices may include a liquid crystal display (LCD) device, a plasma display panel (PDP) device, a field emission display (FED) device, and an organic light emitting display (OLED) device.
Among these, the organic light emitting display device has a competitive edge over others because it does not require a separate light source and enables realization of a compact device design and vivid color display.
Such an organic light emitting display device essentially requires the formation of an organic emission layer. Conventionally, a deposition method using a shadow mask has been used to form the organic emission layer.
However, alternatives are required, because the shadow mask undergoes a drooping phenomenon due to the weight thereof when it has a large area, and thus is difficult to use multiple times and causes defective formation of an organic emission layer pattern.
One of several methods proposed to replace the shadow mask is a tandem-type white organic light emitting device (hereinafter referred to as a “white organic light emitting device”). Hereinafter, the white organic light emitting device will be described.
The white organic light emitting device has features such that a light emitting diode is formed by depositing respective organic layers between an anode and a cathode without using a mask and such that the organic layers including an organic emission layer are sequentially deposited using different components under a vacuum state. In addition, the white organic light emitting device includes different emission layers, which emit multiple colors of light, between the anode and the cathode, and a charge generation layer is provided between the respective emission layers so that stacks are divided from each other on the basis of each emission layer, which is a basic structure.
The white organic light emitting device described above does not emit light using one material, but realizes light emission by multiple emission layers located at different positions in the device, the emission layers including emissive materials having different photoluminescence (PL) peaks for each wavelength, white light being generated via the combination of light emitted from the multiple layers. In one example, a stack including a fluorescent layer and a stack including a phosphorescent layer may be stacked one above another to realize the white organic light emitting device.
However, stack structures known to date have failed to achieve sufficient efficiency of the white organic light emitting device and have different efficiency for each color, thus undergoing variation in color characteristics during long-time driving. In addition, sufficient color gamut may not be realized upon display.